of in situ behaviour of genetically engineered bacteria in standardised
The successful application of bioremediation technology for degradation
of environmental pollutants may require that genetically modified micro-organisms
be introduced into the environment. Because of their perceived novelty,
it is necessary to evaluate such GMOs for any potential risks associated
with their release into the environment. It is also necessary to assess
their survival and ability to degrade pollutants.
Approach and methodology
Two pollutant-degrading, genetically modified micro-organisms were studied.
Both carried genetic modifications affecting the catabolic pathways for
degradation of substituted aromatic compounds. The strains were introduced
into contained activated sludge and soil microcosms, and their behaviour
was evaluated. Three factors were assessed: first, the effects of physico-chemical
and biological variables on the survival and activity of the strains;
second their ability to degrade pollutants in situ; and third the
frequency of transfer of recombinant DNA from the strains to other micro-organisms.
The third of these phenomena was evaluated as a risk associated with the
introduction of the GMO into the environment.
Main findings and outcome
The strains survived in activated sludge and in sterile soil. However,
survival depended on the physico-chemical and biological conditions. The
modified strains degraded pollutant compounds added to the microcosms
via the modified degradation pathways. The genetic material introduced
into the chromosome of these GMOs did not transfer to other micro-organisms.
However, recombinant DNA on plasmids could be transferred to other micro-organisms
and expressed. Transfer maintenance and expression of the DNA was dependent
on the type of recipient micro-organism. The rate of transfer was also
dependent on the nutrient level in the environment, the temperature, and
the degree of agitation. This work demonstrates that genetically modified
micro-organisms can be used for bioremediation.
This work was the first to demonstrate that genetically modified organisms,
in this case micro-organisms, specifically designed to degrade pollutant
compounds did indeed express the desired activities, and thereby degrade
the target pollutants in conditions found in the environment. The project
thus confirms that GMOs may have a contribution to make in cleaning up
environmental pollution. However, to ensure containment of the introduced
genes, any recombinant DNA should be integrated into chromosome of the
modified strains, and not carried on plasmids.
January 1989 December 1990
National Research Centre for Biotechnology (GBF)
Estación Experimental del Zaidín